Clopidogrel is a potent, irreversible thienopyridine-class antiplatelet agent. It is a prodrug that requires hepatic biotransformation to its active metabolite, which selectively and irreversibly inhibits the P2Y12 subtype of the ADP receptor on platelets. This prevents ADP-mediated activation of the glycoprotein GPIIb/IIIa complex, thereby inhibiting platelet aggregation. It is a cornerstone in the secondary prevention of atherothrombotic events, particularly in patients with Acute Coronary Syndrome (ACS) or those undergoing Percutaneous Coronary Intervention (PCI).
Adult: Secondary Prevention: 75mg once daily. Acute Coronary Syndrome/PCI: Loading dose of 300mg to 600mg, followed by 75mg once daily. Typically given with aspirin (75-100mg).
Note: Can be taken with or without food, at the same time each day. Tablet should be swallowed whole with a glass of water. Do not crush or chew.
Clopidogrel is an inactive prodrug. After oral administration, it is absorbed and undergoes a two-step oxidative biotransformation in the liver, primarily mediated by the CYP2C19 enzyme, to generate an active thiol metabolite. This active metabolite forms a disulfide bridge with the P2Y12 subtype of the ADP receptor on the platelet surface. This binding is irreversible for the lifespan of the platelet (7-10 days). By inhibiting the P2Y12 receptor, clopidogrel blocks ADP-induced activation of the glycoprotein GPIIb/IIIa complex, which is the final common pathway for platelet aggregation induced by multiple agonists (ADP, collagen, thrombin).
Pregnancy: Category B: Animal studies show no risk, but no adequate, well-controlled studies in pregnant women. Use only if clearly needed, weighing benefits against potential fetal risk, especially near delivery due to bleeding risk.
Driving: No known effects on driving ability. However, dizziness has been reported rarely.
| Aspirin, NSAIDs (Ibuprofen, Diclofenac) | Increased risk of gastrointestinal bleeding. | Major |
| Oral Anticoagulants (Warfarin, NOACs) | Markedly increased risk of bleeding. | Major |
| Proton Pump Inhibitors (Omeprazole, Esomeprazole) | May reduce antiplatelet effect by inhibiting CYP2C19. Pantoprazole is preferred if PPI is needed. | Moderate |
| CYP2C19 Inhibitors (Fluconazole, Voriconazole, Cimetidine, Fluvoxamine) | May reduce formation of active metabolite, decreasing efficacy. | Moderate |
| CYP2C19 Inducers (Rifampicin, Carbamazepine, Phenytoin) | May increase formation of active metabolite, potentially increasing bleeding risk. | Moderate |
| Other Antiplatelets (Ticagrelor, Prasugrel) | Not used together; excessive bleeding risk. | Major |
| Selective Serotonin Reuptake Inhibitors (SSRIs) | Increased bleeding risk due to impaired platelet serotonin uptake. | Moderate |